(1) Field of the Invention
The present invention relates to a highly strong, highly attrition-resistant alumina catalyst carrier and its manufacturing process.
(2) Prior Art
It is well-known that a catalyst in which platinum or the like as catalytic element is carried on a carrier of alumina or the like has been in use for purification of auto exhaust gas. This catalyst is required not only to function as such, but also to have a certain level of warm-up ability and attrition-resistance, because it has to be able to become normally effective within a specific time after engine starts and also has to be able to endure the running vibration. The catalyst carrier usually meets these requirements.
Alumina-base catalyst carrier has been found as the one which best exhibits an excellent performance as the catalyst. Its conventional manufacturing process consists in partially dehydrating aluminum hydroxide as obtained by the Bayer process; crushing or granulating the product; and then curing it under saturated steam pressure followed by drying and firing. However, if the catalyst carrier thus produced is to have a strength above a specific level, its density must be increased, which will increase the catalyst weight. Meanwhile, an increased density will heavily decrease the warm-up ability of the catalyst bed.
The present invention provides a catalyst carrier free from the above-mentioned defects, which excels both in warm-up ability and in attrition-resistance, and its manufacturing process.